The fastener industry continues to improve the integrity of blind rivets, forming such rivets from a variety of materials as well as meeting a broad range of requirements dictated by various applications. Generally, a blind fastener or blind rivet includes at least a rivet sleeve, a mandril and a locking mechanism, and is used to fasten two or more pieces of material together (the workpiece) when only one side is accessible.
The improvements in the integrity of blind rivets present a problem when such a rivet needs to be removed from the workpiece. When a rivet needs to be removed from the workpiece, the rivet structures must be disassembled to disengage the rivet from the workpiece. The most common method for removing blind rivets from a workpiece is by drilling into the rivet. In this technique, a drill is used to drill out the core of the blind rivet thereby removing material which provides the mechanical strength and characteristics of the rivet to fasten the pieces of material together. As might be expected, this process is somewhat inaccurate, and it is difficult to remove blind rivets from a workpiece in this manner without damaging the workpiece.
One of the problems with removing a blind rivet is that the blind side is often inaccessible. When the rivet is drilled out to remove it from the workpiece, the rivet sleeve tends to engage the drill. This engagement may cause the rivet sleeve to spin within the workpiece bore. Rotary motion or spinning of the rivet sleeve within the workpiece bore during the drilling operation can enlarge the bore and cause damage to the workpiece. Thereafter, different, larger rivets will be needed to assure a secure fastening together of the materials. Additionally, positioning the drill tip on the central longitudinal axis of the rivet and maintaining the drill tip in this position during drilling is difficult. Should the drill bit become displaced from the longitudinal axis of the rivet head, the drill bit may skid across the surface of the workpiece. Of course, when the drill bit skids across the surface of the workpiece, the rotating drill bit can damage the workpiece.